In conventional flexographic printing operations, a supply of ink is transferred to and imprinted on a traveling substrate via a series of rotating rolls in sequential peripheral contact with one another. The series of rolls includes a so-called anilox roll which rotates through an enclosed ink chamber in order to take up a film of ink across the width and about the periphery of the anilox roll. The anilox roll in turn is disposed in peripheral contact with a printing roll, often referred to as a plate cylinder, for transferring ink in a metered thin film onto the printing roll for imprinting onto the substrate.
Anilox rolls are engraved, typically either by a mechanical or a laser engraving operation, to produce an array of recesses circumferentially about the peripheral surface of the roll, commonly referred to as “cells.” The size, shape and depth of each cell and their relative arrangement and spacing over the peripheral surface of the anilox roll principally determine the thickness or thinness and uniformity of the ink film transferred to the printing roll.
Traditionally, anilox rolls have been fabricated of a cylindrical body of steel or other metallic material with a metallic or ceramic peripheral surface capable of being engraved with a desired cell configuration. An axial drive shaft extends from opposite ends of the cylindrical body for mounting within journaled bearings of a printing press. In more recent years, anilox rolls have sometimes been fabricated in the form of a sleeve mountable onto a drive mandrel in a printing press.
Anilox sleeves offer potential advantages over anilox rolls in weight reduction, attendant ease of handling, and lower cost, but also pose potential disadvantages as the sleeve configuration is more susceptible to a loss of circularity and concentricity and more susceptible to damage. Accordingly, it has been conventional practice to fabricate anilox sleeves with a base of non-metallic layers, e.g., a layered configuration of fiberglass, foam and resins, but with an outer metallic cladding layer, typically aluminum, over the full circumferential periphery and ends of the roll. The non-metallic base provides a degree of resilient expansibility radially under the action of compressed air transmitted through the drive mandrel of a printing press to facilitate slidable mounting of the anilox sleeve onto the mandrel and radial gripping compression about the mandrel upon cessation of the compressed air feed. The metal cladding is generally effective to maintain circularity and concentricity and to protect against damage, and provides a reliable bonding surface for an engravable outer ceramic layer. However, the use of metal cladding adds to the weight and cost of the sleeves thereby mitigating to an extent the potential advantages of a sleeve configuration.
It has been proposed and attempted to fabricate anilox sleeves without metal cladding in order to achieve the maximum benefits of weight and cost reduction. Attempts at such so-called “cladless” sleeves however have been found to be particularly susceptible to loss of circularity and concentricity and to damage from handling. In particular, anilox sleeves can often be subjected to rough handling in the environment of a conventional printing operation due to their relatively lighter weight. Cladless sleeves are especially susceptible to damage to their end edges from being stored in a standing disposition and from contact with the abutment surfaces of a mandrel or a storage rack. Accordingly, to date, cladless anilox sleeves have not met with general acceptance and success within the industry.